This invention relates to an endoscope used for observing, for example, the inside of a piping of a water supply and drainage, and more particularly to an improvement of an insert tube structure of the endoscope.
A regular endoscope comprises an operating body and a flexible insert tube structure extending from this operating body. The insert tube structure includes a base portion occupying a large part of an entire length dimension of the insert tube structure and an angle portion extending from a distal end of the base portion and bendable by remote control from the operating body. The base portion of the insert tube structure includes a flex formed by spirally winding a metal strap plate, a cylindrical braid of metal fine wires jacketed (or placed) on an outer periphery of the flex, and a soft resin tube jacketed on an outer periphery of the braid. The angle portion of the insert tube structure includes joints rotatably connected to each other, a cylindrical braid of metal fine wires and jacketed on outer peripheries of the joints, and a soft resin tube jacketed on the braid.
In the case where the endoscope thus constructed is used for observing, for example, the inside of a piping of a water supply and drainage, the insert tube structure of the endoscope needs to have a good slidability, as well as a sufficient amount of flexibility. In the above endoscope, however, since the outer periphery of the insert tube structure is formed of a soft resin tube, slidability is bad and the soft resin tube is susceptible to scratch.
There is proposed another insert tube structure of an endoscope, as disclosed in Japanese Laid-Open Patent Application No. Sho 60-66219, in which a cylindrical braid formed of metal fine wires is additionally placed on the outer side of the resin tube as a jacket, so that the soft resin tube can be prevented from being scratched while allowing it to maintain a sufficient amount of flexibility.
However, the insert tube structure of an endoscope of the above publication has the shortcoming that since the fine wires of the jacket are readily caught by projections in the piping, it is difficult to obtain a smooth reciprocal operation of the insert tube structure in the piping. Another shortcoming had by this conventional structure is that the fine wires, which have been accidentally cut off, are occasionally liable to scratch an inner wall of the piping as well as the soft resin tube of the insert tube structure.